1. Technical Field
The invention relates to pneumatic tires and, particularly to a pneumatic safety tire, which has a wall stiffness such that when the tire is punctured during running, the tire can bear the load of the vehicle to allow for continued relatively high speeds for a relatively long distance under normal highway driving conditions until the proper repair or tire replacement can be made. Preferably, the invention relates to such a safety tire having a high profile with a section height of at least 5 inches.
2. Background Information
Various tire constructions have been devised over the years which enable a tire to run in an under-inflated or non-inflated condition such as after receiving a puncture and loss of pressurized air for extended periods of time and at relatively high speeds, to enable the vehicle operator to safely drive the vehicle to an appropriate location for repair or replacement of the punctured tire. Certain of these safety tires, referred to as "run flat tires", have been successful for certain applications and certain types of tire constructions. Most of these run flat tires achieve the run flat capability, by the placement of reinforcing layers or members of relatively stiff elastomeric material in the side walls of the tire which enable the tire to support the vehicle weight even with the complete loss of internal air pressure.
Examples of various prior art run flat tire constructions are set forth in the following patents:
U.S. Pat. No. 3,911,987 discloses a low profile motorcycle tire which has an elastomeric internal reinforcement so that the tire stays inflated for a short duration with little or no air pressure. The reinforcing layer has a Shore A hardness of at least 45, preferably outwardly of two tire body carcass plies or within the two carcass plies. This elastic reinforcement is constructed with a varying thickness cross-section so as to eliminate abrupt changes of effective hardness of the side wall and reinforcing layer.
U.S Pat. No. 3,949,798 discloses another run flat tire construction for a low profile tire having reinforcing rubber insert strips located between the inner liner and body ply carcass of the tire side wall.
U.S. Pat. No. 3,954,131 discloses a safety tire which has elastomeric internal reinforcements in the side walls to allow the tire to be used for short durations with little or no air pressure within the tire. The elastomeric side reinforcements of the FIG. 4 embodiment are of various thicknesses and are positioned outwardly of the tire carcass.
U.S. Pat. No. 4,067,372 discloses a pneumatic radial tire having internal reinforcements in its side walls which are formed of hard rubber and are used in combination with the body carcass plies and tire bead rubber inserts to give additional stiffness to the supple portions of the tire. The body carcass plies are located outwardly of the rubber inserts and are made from several cord fabric radial plies, and extend completely to the bead area of the tire.
U.S. Pat. No. 4,202,393 discloses a low profile motorcycle tire that has side wall reinforcements to allow for a run flat condition in which the reinforcements are composed of an elastic filler with a reinforcing ply position completely around the elastic filler.
U.S. Pat. No. 4,203,481 discloses a run flat tire construction having reinforcing inserts made from a high modulus, low hysteresis rubber compound, which are located inwardly of the reinforcing carcass plies of the tire.
U.S. Pat. No. 4,261,405 shows another run flat tire construction for a low profile tire having a specially constructed rubber insert mounted between the innerliner and body ply carcass in the side wall of the tire, in order to achieve the required rigidity for supporting the vehicle in an uninflated tire condition.
U.S. Pat. No. 4,265,288 discloses a pneumatic safety tire having rubber inserts mounted in the side walls thereof to provide the required run flat stiffness. The rubber inserts have a JIS hardness of not less than 70, a tensile stress less than 10 kg/cm.sup.2, and an elasticity by Dunlop tripsometer of not less than 65%.
U.S. Pat. No. 4,287,924 discloses another run flat safety tire with side wall reinforcing members. These members are comprised of two components, one of which is more flexible than the other, having a hardness rating greater than 70 and the other having a hardness rating of between 80 and 95. These reinforcing members are encased in the carcass plies of the tire and have a heat conducting layer positioned between the two components of the supporting members to alleviate heating problems in the thickest portions of the supporting members.
U.S. Pat. No. 4,365,659 discloses a run flat safety tire which has side wall reinforcements made from low heat buildup rubber which are positioned between an inner protective layer and the outer carcass plies of the tire.
U.S. Pat. No. 4,917,164 discloses the use of crescent-shaped reinforcing layers in the side walls of the tire to allow the tire to run for short durations with little or no air pressure. The reinforcing layers are of varying thickness and have a Shore A hardness of between 65 and 85, and are positioned between the innerliner and carcass plies of the tire. The wall thickness of the reinforcing members is between 1 and 12 millimeters.
U.S. Pat. No. 4,929,684 discloses a pneumatic tire having greater side wall stiffness for improved handling and performance. This stiffness is achieved directly by the composition of the side walls and not by the use of separate elastomeric inserts.
U.K. Patent Application GB 2 138 367 A discloses a pneumatic tire having run flat capabilities in which an elastomeric insert having an ISO hardness not exceeding 37 and a particular thermal stability is mounted between two of the radial carcass body plies in order to provide the side wall stiffness for running in an uninflated condition.
Although many of these run flat tire constructions set forth in the above described patents, have proved to be successful for certain applications, all of these construtions pertain to low profile tires, that is a tire having a section height less than 5 inches and are of the type usually found on high performance vehicles or motorcycles, to which the above referenced patents pertain, and rely almost entirely on the stiffness of the elastomeric insert to provide the support for the uninflated tire. Furthermore, these high performance tires and motorcycle tires carry relatively smaller loads when compared to the higher weights carried by the larger cars using the higher section height tires.
Heretofore, the providing of a run flat tire for a high profile tire construction, that is a tire having a section height of 5 inches or greater, has not proved successful due to the relatively large side wall reinforcement members which would be required to adequately support the tire in an uninflated condition to enable the tire to run for a relatively long distance at a relatively high rate of speed. The relatively large rubber inserts which would be required would increase the weight of the tire to an unacceptable limit and would materially detract from the ride characteristic of the tire. If the amount of the material or type of material in these relatively large side wall inserts were reduced or changed in order to lessen the weight of the tire and improve the ride characteristics for high section height tires, excessive heat would be generated within the inserts during a run flat condition due to the increased tire deformation, resulting in the rapid destruction of the tire, thus preventing the desired run flat capabilities from being achieved at usual highway speeds for satisfactory use on such tires on most passenger vehicles.
Thus, the need has existed for a pneumatic safety tire or run flat tire, preferably for high profile tires, that is a tire having a section height of 5 inches or greater, which heretofore has not been achieved by the use of the various constructions and technology presently used for the construction of run flat tires having a low profile, and to such a safety tire in which the required side wall stiffness is achieved by a combination elastomeric insert and a reinforcing bias ply strip which also improves the low profile run flat tire construction.